Edit based on comment thread:
You could push a script to everyone with Apple Remote Desktop that attempts to mount a sharepoint. Or, as you said above, Apple does provide a password changing website, but again, that would require emailing everyone and telling them to go to the website, which many might ignore.
How to set up an OD user who doesn't have a network home folder:
- Create the user in Workgroup Manager.
- Click on "Home" in the segmented control bar at the top.
- Click the plus button, leave the first two fields blank, and type /Users/username, where you would replace username with the short name of the user. At this point, you'd want to make sure that the user you're setting up doesn't already have a local account with the same name.
- Click Okay, then make sure that the entry you created is selected. It should have a harddrive icon and be listed as /Users. Click "create home now", then click save.
That's it! If you don't specify that the user should get a local folder and leave it as no home folder, you'll actually be unable to log in at all. Now you have all of the management you'd get with having a bound Machine and a network account, without the extra storage overhead (and possible long login times).
Old answer: I don't want to seem condescending but you really need to learn more before you jump into this. The Lynda training series videos for snow leopard server are great, or grab a book from the bookstore. Snow Leopard Server is very picky. Everything needs to be set up properly and in a very specific order. The best advice I can give you is to start fresh - open up a book or start the video and start from the beginning. Set up DNS exactly how they say, then wipe and reinstall OS X server (remember to run software update!) and go from there with a fresh start. I myself had to do that several times on a test server before I got the process down right.